Tracking Santa

December 24, 2010

Each year since 1955, Norad has tracked Santa Claus on his annual journey to deliver toys to good little girls and boys around the world. Since Santa must file his flight plan in advance, we already know where his journey will take him: the route at http://www.noradsanta.org/js/data.js is reproduced on the next page.

Your task is to calculate the number of miles that Santa will travel during his journey; you might find Wikipedia’s Great-circle distance page helpful. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.

A few days late, but here’s my Python
version. I went with the arctangent formula given by Wikiepdia, which it calls
“a more complicated formula that is accurate for all distances.” I also followed
Jebb’s lead of saving “data.js” with the var locations = portion
removed. This can be run (at least on my system) with ./santa.py data.js.

Download the data.js and save to santaflightpath.py. Edit the first line to remove “var “, so it starts with “location =”.
Remove the “;” from the last line. This creates a python compatible statement defining ‘locations’ to be a list of dictionaries. Importing ‘santaflightpath’ executes the code in the file, so there are clearly security implications.

pairwise is from the recipies in the itertools documentation.

Of interest, the flight plan is 28 hours long; stays within 600 miles of the north pole for the first 4 hours; doesn’t appear to visit Antarctica; and doesn’t return to the starting point.